port test_extensions into v3 part1

This changeset only copies the v2 files into the appropriate v3
directories unchanged. This is being tried in order to make
reviewing of the porting easier as gerrit will display only what
is actually changed for v3 rather than entirely new files.

Partially implements blueprint nova-v3-api-tests

Change-Id: I071c4e6ff3d36d4cbfe7a7a27885ddf013a52b8c
Merge "port test_extensions into v3 part1"